If you've tried to evaluate surgical skin preps, you know it's no easy task. The FDA's proposed efficacy standards have been in limbo for a decade, and product information can be hard to find. To help you better understand the properties of these preps, we gathered information from manufacturers and compiled our One-Stop Guide to Surgical Skin Preps. Before reading the pullout guide on the next page, here are some things you need to know:

There are no universal efficacy or safety standards. The FDA's last regulatory proposal dates back to 1994 (Tentative Final Monograph, or TFM). It proposed specific efficacy tests and categorized prep ingredients by their known safety and efficacy, with category I products "generally recognized as safe and effective," category IIs "not recognized" and category IIIs requiring "further testing." But because the TFM is still a draft, some manufacturers are in regulatory limbo. For now, the operating philosophy is that manufacturers can market ingredients listed in the TFM (whether category I or III) without undergoing the proposed efficacy tests, giving them leeway to determine just how to test. Further, makers of combinations of individually listed TFM ingredients or slightly varied formulations simply aren't sure what they're supposed to do. The only thing FDA has made clear is that preps containing newer, clearly unlisted ingredients or chlorhexidine gluconate require rigorous New Drug Application approval.

Efficacy. We asked manufacturers if their products meet the proposed TFM standards for in vitro and in vivo efficacy. In terms of in vitro efficacy, the FDA proposes evaluating the antimicrobial spectrum of activity on a very specific collection of gram (-) and ( ) organisms and yeasts at intervals between one minute and 30 minutes. The faster the kill rate, the better your margin of safety.

In terms of in vivo efficacy, the FDA proposes a standard of 2 log reductions of bacteria per cm2 on dry sites (abdomen) and 3 log reductions on moist sites (inguinal) within 10 minutes of prepping, with continued antimicrobial effect (persistence) for six hours. Since each log reduction is an exponent of 10, a 2-log reduction is equivalent to a 99 percent reduction and a 3-log reduction is 99.9 percent equivalent. Since results can fluctuate due to variables like skin flora, application technique, contact time and volume of solution, we asked only if each product meets the proposed standard.

• Prices vary. Since cost varies with volume, GPOs and other factors, we didn't include list prices. Here are product types by least to most expensive: traditional povidone-iodine solution; chlorhexidine gluconate; one-step solutions.
• Other factors matter. We asked manufacturers about characteristics like water solubility, staining, contact/drying times, irritant levels and interactions. The feedback will let you know if you'll need special removal solutions, if the prep can be seen on the skin, and if clothes and OR surfaces might stain. You'll also know how long each prep should take to use and whether blood, saline or alcohol challenges can weaken or inactivate the prep.

Two things industry experts want you to keep in mind when reading the pullout guide: First, follow manufacturers' instructions, or efficacy can suffer and the prep might not do the job it promises. Second, efficacy criteria for hand scrubs are different, because the challenges and environment (under gloves, for example) differ.

We hope this chart helps you make the best decisions for your and your patients' needs.